Fluvial Sand, Botswana stream
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Metsimotlhabe river | Glass bead is 200µ in diameter |
Location |
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Metsimotlhabe river (Kumakwane~25 km from Gaborone), Botswana along the river bed. (Latitude |
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-24.69S and Longitude 25.71E) |
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Depositional facies | River bed |
Provenance |
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The river flows through waterberg group of rocks, which are an assemblage of sandstones, |
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conglomerates and siltstones. This is continental red bed sediments |
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Composition |
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Predominantly coarse grained quartz with a few grains of chert and rock fragments, |
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dominant typically blocky, equant, translucent and milky-white, rarely |
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yellowish monocrystalline |
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quartz. |
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Rare transparent clear quartz |
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crystals; trace quantitites of epidote, rutile, zircon, sphene |
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and possibly garnet. |
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Most grains are coated with an FeOx cutane. FeOx minerals (goethite ?) precipitated repeatedly from |
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groundwater after sand was occasionally moistened and capillary water evaporated |
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Texture |
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Medium-grained (mL, 250-350µ), poorly sorted, subangular-subrounded |
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Petrographic thin section:
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Description | insert here short description of thin section |
insert here a bright field image |
| insert here a dark field image |
Bright field | Dark field |
Sample number |
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Sample Number:
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heubeck0140 | |
Collector |
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Elisha M. Shemang, |
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Dept. of Geology, University of Botswana |
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Date |
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of sampling | 11.01.2008 |
Comments:
Mineral color in quarz quartz is due to impurities of rutile, Tourmaline tourmaline or Fe-Oxides oxides intergrown
with the quartz crystal. Additionally, gas and liquid bubbles trapped during crystallization reduce transparency transparency.
